如何在Django中验证模型中的一个字段？

from django.core.exceptions import ValidationError

def validate_length(value):
    if len(value) > 10:
        raise ValidationError('字段长度不能超过10个字符')

class MyModel(models.Model):
    my_field = models.CharField(max_length=20, validators=[validate_length])

from django.core.exceptions import ValidationError

class MyModel(models.Model):
    my_field = models.CharField(max_length=20)

    def clean_my_field(self):
        value = self.cleaned_data['my_field']
        if not value.startswith('ABC'):
            raise ValidationError('字段格式必须以ABC开头')
        return value